With increased commercial interest in the Internet and the World Wide Web (WWW), the networked delivery of content has become commonplace. Existing content delivery systems are typically based on a client-server model, implemented with web-servers and web-clients that communicate via the Hypertext Transfer Protocol (HTTP). Many formats for the representation of content are known in the art, including Hypertext Markup Language (HTML), Extensible Markup Language (XML), Postscript™, Portable Document Format (PDF), Shockwave™ Format (SWF), Microsoft Word™, WordPerfect™, text, MPEG, JPEG, TIFF, AVI, and so on.
Existing content-delivery systems, and the content representation formats they rely on, present a number of problems. A first problem relates to the complexity of existing digital rights management (DRM) technologies. Content that is provided directly to clients in standard formats such as HTML, text, or MPEG may be copied by the client and possibly shared with other, possibly unauthorized users. Digital rights management includes a general class of techniques that can be used to prevent unauthorized access to content. In some DRM approaches, content is encrypted by the content-delivery system and then delivered to clients in encrypted form. Clients then view the content using a secure rendering and/or display component that is capable of decrypting the content for authorized users. However, such theoretically secure content-delivery systems impose a considerable startup cost for the ordinary end-user because they are typically difficult to configure, require an understanding of advanced cryptographic concepts (e.g., public keys, private keys, certificates, etc.), and may not be flexible in the face of changes to the underlying hardware or software of the client computing system. Also, the inclusion of DRM technologies into an application can be prohibitively expensive to a content provider if non-open source or non-freeware solutions are incorporated.
In addition, many existing content representation formats are not capable of representing dynamic content or generating the dynamic display of information. For example, HTML only provides rudimentary facilities for representing dynamic presentation elements, such as animations. This inability to describe and represent dynamic presentation elements makes many content representation formats unsuitable for providing the user with an experience that is tailored to the particular attributes of the target user.
Furthermore, many content representation formats such as Microsoft Word are proprietary and/or opaque, and therefore suffer from a lack of readily available toolkits for programmatically processing and constructing seamless, customized content packages targeted to end-users. These properties can impose substantial barriers to entry and/or lock-in costs on content providers and/or end-users.
Also, the sheer proliferation of content representation formats causes substantial end-user confusion because they need to install, maintain, and upgrade a wide variety of players, renderers, viewers, or interpreters to display the wide variety of available content formats. Format proliferation also plagues the operators of content-delivery systems, because they need to install, manage, and upgrade an ever-increasing array of tools and systems for processing and maintaining source content. Operators of content-delivery systems may also be required to bear the cost of providing technical support and/or training for their users so that the users can effectively install the necessary software to view the various forms of delivered content.